Lithium battery fire danger in the skies
Published: 04 March, 2014
Growing concerns* regarding battery fires on board aircraft means a new Technical Standard Order** from the Federal Aviation Administration is imminent. Jose Sanchez de Muniain speaks with Joe Ashton of AmSafe Bridport about why lithium batteries are of particular concern and what can be done to mitigate the risk.
The TSO will be the result of a standard for fire containment covers for shipping pallets that has been developed by the Society of Automotive Engineers at the request of the Federal Aviation Administration (and which will be mirrored by an identical standard by the ISO).
AmSafe Bridport played a significant part in the development of the standard as a result of its experience in specialist fire protection textile equipment for defence and commercial aviation, including main deck fire barriers; main deck textile smoke partitions; and fabric cargo liners. Once the TSO is issued, it is expected that AmSafe’s Fire Containment Cover will be the first to be fully certified for use on aircraft.
Q: Is the new TSO aimed specifically at lithium battery fires?
The issue of onboard fires has been going for a long time but the coverage it has received has increased ten fold as a result of lithium battery fires, which get all the headlines.
Q: Why are lithium batteries of particular concern?
Crates and pallets of lithium batteries are transported every day and they go through a rigorous dangerous goods procedure to mitigate the risk. But it is the undeclared dangerous goods – the one-off lithium batteries in a consignment – that we are trying to mitigate the risk of fire from. It could be an individual consignment from an online seller that is not aware of the dangerous goods regulations and who just packages the phone or whatever, and then this gets through the system and onboard the aircraft. That lithium battery could quite easily become the ignition source to start a class A fire. And that is where the Fire Containment Cover will provide six hours of protection.
Q. What does the FCC consist of?
It has two elements. The first is an integral certified pallet net that acts as a primary restraint, which is made of lightweight Dyneema. This fibre is fifteen times stronger than steel and it has been coated with flame resistant coating so it will melt and not flame. The net is attached to an intumescent fire cover – effectively fibre glass – which is what contains the fire. What happens typically within the first thirty minutes of a fire is that the heat melts the pallet net, but that primary restraint mechanism is overridden by the concern to suppress the fire.
Q. Is there much oxygen in the hold to feed a class A fire?
There is oxygen and the FCC is designed with a gap at the bottom – and therefore not air tight – for two reasons. Firstly, so that smoke can come out and be detected by the onboard detection systems. It is important that the pilot and crew are aware that there is a problem. The second reason is for decompression purposes – if the aircraft drops altitude quickly as a result of the fire, there could be decompression issues with a sealed unit.
Q. How do you test for this type of cover?
We have carried out a number of independent tests. The fire containment cover’s material meets the requirements of CS-25/FAR Part 25 Appendix F, Part III, PARA (A)(3) (Amendment 25-72)*** for flame penetration resistance. We have also carried out full scale fire tests with a class A fire. This is a full sized pallet of boxes filled with kilos of shredded paper and an ignition source inside one of the boxes. The test measures the temperature at a number of required locations, including fabric surface, pallet surface, and four inches from the surface. The test ends after six hours and in all honesty the fire will still be going. The FCC doesn’t put out the fire – it suppresses it and enables the crews to get the aircraft safely on the ground. If it takes hold when the aircraft is on the ground and everyone is safe – so be it, you have lost an aircraft but everyone is safe.’
Q. Why six hours?
The existing ETOPS (Extended range Twin Operations) FAA requirement for long-range aircraft is for four hours from somewhere it can land. Our first version of the cover provided four hours of protection, but our latest version withstands fire for six hours, in advance of potentially longer-range aircraft, and ETOPS pushing to six hours.
Q. Are any airlines using this type of technology?
We can’t go into specifics, but we have close to 1,000 covers out now and they have been flying operationally for around two years.
Q. Are there any applications for this type of technology in the cabin?
We are looking at this at the moment, and what type of applications could help support fire suppression systems in the cabin. It could be laptop bags or fire suppression bags, which we already have available with one operator. We are investigating how we can integrate this technology into cabin linings, or for instance in overhead bins. Having laptops and mobile phone holders made out of this technology is also something we are discussing.
Q. Where would the incentive come from for this type of application?
There have been a number of fires on board, most of which have been swept under the carpet. A recent report by the BBC about a CAA press release has raised the profile, but typically we have highs and dips as interest rises and wanes. I believe you only need one serious incident caused by a cabin fire for everyone to wonder why this technology wasn’t available. Rather than wait for that to happen, why not look if there is a solution today?
* As of January 3, 2013, 140 air incidents involving batteries carried as cargo or baggage have been recorded by the FAA since March 20, 1991. There are also estimates that the average small plane carrying 100 passengers could have 500 lithium batteries on board.
** A Technical Standard Order (TSO) is a minimum performance standard for specified materials, parts, and appliances used on civil aircraft.
*** Part III – T Test Method to Determine Flame Penetration Resistance of Cargo Compartment Liners. There must be no flame penetration of any specimen within 5 minutes after application of the flame source, and the peak temperature measured at 10 cm (4 inches) above the upper surface of the horizontal test sample must not exceed 204 ºC (400ºF).
**** As per FAA AC20-42C 7A(1).